Method and apparatus for making tobacco smoke filters

Abstract

Tobacco smoke filters and methods and means for making same wherein the products have a composite substantially cylindrical inner member formed from two semi-cylindrical inner elements and overwrapped with a common plug wrap. The composite inner member has a discrete inner cavity formed in each semi-cylindrical element and a composite cavity formed by a depressed portion in each semi-cylindrical element. A substantially smooth outer surface is provided on the composite inner member for attaching a conventional plug wrap without the need for an internal glue line. Separate cylindrical elements are reformed into semi-cylindrical elements and crimped to provide depressed pockets, following which the semi-cylindrical elements are mated and overwrapped to produce the final product.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A method of making smoke filters comprising the steps of: a. providing a first filtering material including a multiplicity of fibrous members;   b. defining a first elongated substantially cylindrical, annular bonding zone;   c. continuously passing said first filtering material through said first bonding zone and during passage of said first filtering material through said first bonding zone contacting same with a bond activating agent to bond said fibrous members of said first filtering material to each other at spaced contact points thereby forming a first elongated, smoke-permeable, cylindrical inner element having an axial bore and an annular wall defining a tortuous path for passage for smoke therethrough;   d. subjecting an arcuate section of the annular wall of said first cylindrical inner element to alternating axially spaced flattening and depressing actions to thereby reform said first cylindrical inner element into a first semi-cylindrical inner element having alternating axially spaced externally flattened portions and externally depressed portions, with said externally depressed portions forming axially spaced sections extending across the interior of said first semi-cylindrical inner element which offer at least as much resistance to passage of smoke as the material of said first semi-cylindrical inner element and which define together with said externally flattened portions a multiplicity of axially spaced, discrete, first cavities within said first semi-cylindrical inner element;   e. providing a second filtering material including a multiplicity of fibrous elements;   f. defining a second elongated substantially cylindrical, annular bonding zone;   g. continuously passing said second filtering material through said second bonding zone and during passage of said second filtering material through said second bonding zone contacting the same with a bond activating agent to bond said fibrous members of said second filtering material to each other at spaced contact points thereby forming a second elongated, smoke-permeable, cylindrical inner element having an axial bore and an annular wall defining a tortuous path for passage of smoke therethrough;   h. subjecting an arcuate section of the annular wall of said second cylindrical inner element to alternating axially spaced flattening and depressing actions to thereby reform said second cylindrical inner element into a second semi-cylindrical inner element having alternating axially spaced externally flattened portions and externally depressed portions, with said externally depressed portions forming axially spaced sections extending across the interior of said second semi-cylindrical inner element which offer at least as much resistance to passage of smoke as the material of said second semi-cylindrical inner element and which define together with said externally flattened portions a multiplicity of axially spaced, discrete, first cavities within said second semi-cylindrical inner element;   i. continuously juxtaposing said first and second semi-cylindrical inner elements to each other with said externally depressed portions of said semi-cylindrical inner elements facing each other to form a composite cylindrical inner member having alternating discrete first cavities and composite second cavities defined by said depressed portions of said semi-cylindrical inner elements;   j. overwrapping said composite cylindrical inner member with an overwrapping material so as to juxtapose portions of the inner surface of said overwrapping material with the outer surface of said composite cylindrical inner member to form sealed areas precluding axial passage of smoke thereacross; and   k. transversely severing the resulting product at selected locations to form filter elements each having at least a portion of two discrete first cavities and at least a portion of one composite second cavity.   
     
     
       2. A method according to claim 1 wherein said first and second filtering materials each comprise cellulose actate tow and said bond activating agents comprise steam. 
     
     
       3. A method according to claim 1 further comprising feeding a further smoke-modifying material into at least one of said cavities. 
     
     
       4. A method according to claim 3 wherein said further smoke-modifying material comprises activated carbon. 
     
     
       5. An apparatus for making smoke filters comprising: a. a source of a first filtering material including a multiplicity of fibrous members;   b. means defining a first elongated, substantially cylindrical, annular bonding zone;   c. means for continuously passing said first filtering material through said first bonding zone and during passage of said first filtering material through said first bonding zone contacting same with a bond activating agent to bond said fibrous members of said first filtering material to each other at spaced contact points thereby forming a first elongated, smoke-permeable, cylindrical inner element having an axial bore and an annular wall defining a tortuous path for passage of smoke therethrough;   d. means for subjecting an arcuate section of the annular wall of said first cylindrical inner element to alternating axially spaced flattening and depressing actions to thereby reform said first cylindrical inner element into a first semi-cylindrical inner element having alternating axially spaced externally flattened portions and externally depressed portions, with said externally depressed portions forming axially spaced sections extending across the interior of said first semi-cylindrical inner element which offer at least as much resistance to passage of smoke as the material of said first semi-cylindrical inner element and which define together with said externally flattened portions a multiplicity of axially spaced, discrete, first cavities within said first semi-cylindrical inner element;   e. a source of a second filtering material including a multiplicity of fibrous members;   f. means defining a second elongated, substantially cylindrical, annular bonding zone;   g. means for continuously passing said second filtering material through said second bonding zone and during passage of said second filtering material through said second bonding zone contacting the same with a bond activating agent to bond said fibrous members of said second filtering material to each other at spaced contact points thereby forming a second elongated, smoke-permeable, cylindrical inner element having an axial bore and an annular wall defining a tortuous path for passage of smoke therethrough;   h. means for subjecting an arcuate section of the annular wall of said second cylindrical inner element to alternating axially spaced flattening and depressing actions to thereby reform said second cylindrical inner element into a second semi-cylindrical inner element having alternating axially spaced externally flattened portions and externally depressed portions, with said externally depressed portions forming axially spaced sections extending across the interior of said second semi-cylindrical inner element which offer at least as much resistance to passage of smoke as the material of said second semicylindrical inner element and which define together with said externally flattened portions a multiplicity of axially spaced, discrete, first cavities within said second semi-cylindrical inner element;   i. means for continuously juxtaposing said first and second semi-cylindrical inner element to each other with said externally depressed portions of said semicylindrical inner elements facing each other to form a composite cylindrical inner member having alternating discrete first cavities and composite second cavities defined by said depressed portions of said semi-cylindrical inner elements;   j. means for overwrapping said composite cylindrical inner member with an overwrapping material so as to juxtapose portions of the inner surface of said overwrapping material with the outer surface of said composite cylindrical inner member to form sealed areas precluding axial passage of smoke thereacross; and   k. means for transversely severing the resulting product at selected locations to form filter elements each having at least a portion of two discrete first cavities and at least a portion of one composite second cavity.   
     
     
       6. An apparatus according to claim 5 wherein said first and second filtering materials each comprise cellulose acetate tow and said bond activating agents comprise steam. 
     
     
       7. An apparatus according to claim 5 further comprising means for feeding a further smoke-modifying material into at least one of said cavities. 
     
     
       8. An apparatus according to claim 7 wherein said further smoke-modifying material comprises activated carbon.